1. Is the ticket perforated? If it is physically perforated it is likely to be legit. Most fakes print the perforation because they make the tickets on a standard printer. To print a ticket with perforated edges requires tech that a scam artist doesn't usually buy.
2. Download the app barcode scanner. Scan the ticket. If some random combination of numbers and letters pop up, you are probably good. If it says dummy barcode you got got.
3. Out of curiosity, where did you buy these tickets. Somewhere reputable like StubHub or somewhere without protection like Craigslist?